Flying discs are well-known as toss toys. When properly thrown, they fly a distance, and then land like an inverted saucer. A normally oriented (upright) saucer can easily be picked up by its outer edge which extends upwards at some angle. However, when a saucer is inverted, the outer edge extends downward, and consequently does not present an edge that is easy to grasp.
A Frisbee® (Registered Trademark of Wham-o, Inc) is a flying disc that can be used as a toss toy. Dogs enjoy chasing, catching, and retrieving such flying discs. However, the standard Frisbee is too hard for use as a toss toy for dogs. Consequently, soft rubbery versions of the Frisbee are sold that are made from a more pliable material that better resists a dog's bite, and prevents possible injury to the dog that may occur with more rigid materials.
Such softer more pliable versions of the Frisbee, and the like, nevertheless retain the same problem of an inverted saucer, i.e., it is hard to pick up by its edge because the outer edge extends downward and contacts the ground. Consequently, when a Frisbee lands properly, it does not present an edge that is easy to grasp by a person's hand.
Further, when retrieving a Frisbee (or the like), dogs have a particularly difficult time picking up the Frisbee when it lands properly, i.e., like an inverted saucer with its outer edge extending downward and contacting the ground all about its circumference. This is because dogs use their mouth to pick up the disc, and a dog's mouth has substantially less dexterity than a person's hand. Thus, the outer edge presents a substantial problem for a dog, making even a soft flexible Frisbee very difficult for a dog to pick up and retrieve.